I own a Marshall Powerbrake, a Weber Mass 100 watt and an Airbrake.
The Marshall is a true piece of junk. It compresses WAY too much and suck all the midrange out.
(too bad, I used it for years not knowing)
The Weber Mass is good if you're looking for large amounts of attenuation. It's texture is a bit different than the Airbrake, not bad, just different. And I think it compresses a bit more than the Airbrake. Also, if you're a gigging player, the Weber Mass has a 6db reduction even when it's turned up the loudest it can go. This is a lot of reduction. If you're looking to reduce the volume just a little bit, this won't work. If you're playing at home or in the studio, it will be fine. But I don't consider it good for the gigging player.
I think the Airbrake is the best. Not because I'm a Z fan, but for the following reasons:
First, It's the most dynamic of the three. You can really feel the notes jump out at you. Very little compression.
Second, there is no reduction in volume if you don't want it. And the first several 'clicks' reduce the volume in small amounts allowing you to really 'dial it in'.
Third, there is no coloration in the sound.
Fourth, you can use it with any ohm rating. (hotplates suck in this regard)
I have never tried a hotplate, so I can't say anything about that.